Crazy rev-counter

[PeteJS]

Hi,

The rev counter on my mk1 Stag over-reads and flicks back wards and forwards around dial.

I've tried cleaning all of the contacts both on the instrument and the wiring connectors, but this made little or no difference.

I've checked that ballast resistor and that seems to work OK, e.g. halves the voltage. I've recently fitted a new coil, condenser and distributor cap also.

I am still running twin points and the car is Federal spec (but not sure that makes a difference) and runs well otherwise.

Any ideas?

Pete

[Andrew S]

Hi Pete

I may be wrong but its on same circuit as the coil so could be showing up a coil fault

Cheers
Andrew

[richardthestag]

mk1 rev counter doesn't like electronic ignition setups

It is possible to make up a Mk1 looking tacho with mk2 guts, will need mods to the connections etc

[TR5convalescent]

Have you fitted electronic ignition? Apparently this changes the signal or something. The cure is to fit a capacitor, but how I don't know. I found a web link and did exactly as it said with a capacitor and a resister and it made things even worse.

[PeteJS]

Thanks for the replies.

I am still running twin points.

I have recently fitted a new coil, with the same result as the old coil.

Will look at hybrid mk1 / mk2 coil when I fit electronic ignition over the winter.

Looking for a quick fix before we set off on road trip around France, next week, mad needle is really off putting..........

[PeteJS]

Is there anything that requires cleaning / adjustment internally?

[richardthestag]

could try a straight swap with another mk1 unit.

[PeteJS]

Had thought of switching it out for another, not got one to hand at the moment, so will have to wait until I'm back from the France trip with the car in a few weeks.

Cheers

[v8ken]

When converting to electronic ignition for mk1 rev counter,I used this-

http://www.ebay.co.uk/itm/Smiths-RVI-RVC-Tachometer-conversion-board-calibration-cable-2016-Design/380578001095?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

works a treat,and still keeps your original instrument.(you have to connect an extra wire from the coil'as mk2 wiring')
Ken.

[wilf]

When playing with USA (MSD) ignitions years ago, I found they too needed help to drive some Smiths tachos, and this page has some converters that might do the trick:

https://www.msdperformance.com/products/accessories/tach_adapters/

Incidentally, I got great results on RV8s and yank small blocks with their electronic ignitions. Surprised no-one ever recommends them for Stags.

[StagManiac]

I've wondered about MSD systems on Stags. I have been reading American car magazines, custom car magazines and kit car magazines for a long time. MSD systems are popular in the USA.

Paul

[wilf]

Almost standard fit in the kit car world............. and because they are a CDI unit, you fit one of their "blaster" coils and forget any ballast/coil/ignition issues and just enjoy big fat sparks all the time. In my last 7 litre V8 I built, I could open the plug gaps up to over 60 thou and they still fired!

If my lumenition ever gives up, this is what I will fit.